function y = em(x)
%Extended Maratos Function 
%x0=[1.1, 0.1, ...,1.1, 0.1].  
%fmin=n/2
%Author:shi yangyang
n=length(x);
m=n/2;
c=100;
y=ones(1,m);
for i=1:1:m
    t1=x(2*i-1)^2+x(2*i)^2-1.0;
    y(i)=(x(2*i-1)+c*t1*t1);
end
y=sum(y);